Enhanced Frequency Stability in Real Microgrids Through Three-Phase Droop Control With Dead-Band and Ramp-Rate-Constrained Hydrogen Operation

Abstract

This paper proposes a modeling, simulation, and operational analysis framework for the conversion of an electrical distribution network into a microgrid (MG) integrating renewable energy sources, battery energy storage, and green hydrogen technologies. The proposed framework targets enhanced operational resilience and frequency-voltage stability under islanded conditions, which are critical requirements for modern active distribution networks with high penetration of inverter-based resources (IBRs). The considered MG comprises three IBRs with complementary operational roles: a battery energy storage system (BESS), a photovoltaic (PV) generator, and a green hydrogen (GH2) fuel cell, providing coordinated active and reactive power support. A three-phase droop control strategy incorporating frequency and voltage dead-band regions is adopted to reduce unnecessary control actions under small disturbances while accounting for practical converter power limits and ramp-rate constraints. To further improve the operational performance, an optimal power flow (OPF) formulation coordinates the dispatch of the IBRs, reducing excessive battery utilization and reactive power support while maximizing renewable energy participation. The individual contribution of the proposed dead-band mechanism is isolated through a direct comparison with conventional continuous droop control under identical operating conditions, complemented by a sensitivity analysis to identify the adopted dead-band design and systematically evaluate the interaction between the control and optimization layers. The proposed approach is validated using a real electrical distribution feeder modeled in OpenDSS. Steady-state power flow analysis indicates a total active power of 22.17 MW, reactive power of 10.14 Mvar, and active power losses of 2.47%. The most critical operating condition occurs at 13:00, when peak demand coincides with a minimum voltage level of 0.92 p.u., highlighting the need for coordinated voltage control strategies. To alleviate these operating constraints, a portion of the feeder is disconnected from the main grid and operated as an islanded MG supplied by PV, BESS, and GH2 resources, reducing the operational burden on the remaining distribution feeder while improving local operational performance and resilience. Compared with conventional continuous droop control, the proposed dead-band strategy reduces the normalized time-weighted frequency deviation by 84.6%, the cumulative frequency excursion by 78.9%, and PV curtailment by 51.6%, while maintaining OPF convergence in all simulated operating conditions. These improvements are achieved with only a modest increase in the maximum voltage deviation. The results demonstrate the effectiveness of the proposed integrated control and energy management framework for enabling resilient and coordinated operation of islanded MGs integrating PV, BESS, and GH2 resources.